Continuous interconnects between heterogeneous materials

ABSTRACT

A structure may include a first material, a second material joined to the first material at a junction between the first and second materials, and one or more media extending across the junction to form a continuous interconnect between the first and second materials, wherein the first and second materials are heterogeneous. The structure may further include a transition at the junction between the first and second materials. The one or more media may include a functional material which may be electrically conductive. The structure may further include a third material joined to the second material at a second junction between the second and third materials, the media may extend across the second junction to form a continuous interconnect between the first, second, and third materials, and the second and third materials may be heterogeneous.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims the benefit of U.S. Provisional PatentApplication No. 63/201,916, filed May 18, 2021, which is incorporated byreference herein in its entirety.

BACKGROUND

The inventive principles of this patent disclosure relate generally tointerconnects between two heterogeneous materials, and more specificallyto structures having one or more media extending between twoheterogeneous materials to form a continuous interconnect between thematerials, and/or methods of forming such structures.

SUMMARY

A structure may include a first material, a second material joined tothe first material at a junction between the first and second materials,and one or more media extending across the junction to form a continuousinterconnect between the first and second materials, wherein the firstand second materials are heterogeneous. The structure may furtherinclude a transition at the junction between the first and secondmaterials. The transition may include a lap joint. The one or more mediamay include a functional material. The functional material may beelectrically conductive. The functional material may include aconductive gel. The first material may be substantially more rigid thanthe second material. The first material may be substantially moreelastic than the second material. The structure may further include afirst encapsulant arranged on the first material to substantiallyenclose a portion of the media. The structure may further include asecond encapsulant arranged on the second material to substantiallyenclose a portion of the media. The first material may include a viathrough which at least a portion of the media passes. The structure mayinclude a lap joint at the junction between the first material and thesecond material, and the via passes through the lap joint. The structuremay further include an electric component attached to the first materialand electrically coupled to the media.

The junction between the first and second materials may include a firstjunction, the structure may further include a third material joined tothe second material at a second junction between the second and thirdmaterials, the media may extend across the second junction to form acontinuous interconnect between the first, second, and third materials,and the second and third materials may be heterogeneous. The media maybe electrically conducting, and the structure may further include afirst electric component attached to the first material and electricallyconnected to the media, and a second electric component attached to thethird material and electrically connected to the media.

A sensor structure may include a first substrate comprising a firstmaterial, a conductive contact layer comprising a second materialdisposed on the first substrate, a second substrate comprising a thirdmaterial disposed on the first substrate, and a conductive gel arrangedin a pattern on the second substrate and forming a continuous electricalinterconnect with the conductive contact layer, wherein at least two ofthe first, second, and third materials are heterogeneous. The sensorstructure may further include an electric component disposed on thesecond substrate and electrically connected to the continuous electricalinterconnect. The first substrate may include a via through which thecontinuous electrical interconnect connects to the conductive contactlayer.

A method may include joining a first material to a second material at ajunction, and forming a continuous interconnect between the first andsecond materials across the junction, wherein the first and secondmaterials may be heterogeneous. The method may further includeencapsulating the continuous interconnect.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures are not necessarily drawn to scale and elements of similarstructures or functions may generally be represented by like referencenumerals for illustrative purposes throughout the figures. The figuresare only intended to facilitate the description of the variousembodiments described herein. The figures do not describe every aspectof the teachings disclosed herein and do not limit the scope of theclaims. To prevent the drawings from becoming obscured, not all of thecomponents, connections, and the like may be shown, and not all of thecomponents may have reference numbers. However, patterns of componentconfigurations may be readily apparent from the drawings.

FIG. 1 illustrates an embodiment of a structure according to some of theinventive principles of this patent disclosure.

FIG. 2 illustrates another embodiment of a structure according to someof the inventive principles of this patent disclosure.

FIG. 3 is an exploded perspective view illustrating an exampleembodiment of an interconnect design according to some inventiveprinciples of this disclosure.

FIG. 4 is a cross-sectional view of another example embodiment of aheterogenous structure according to some inventive principles of thisdisclosure.

FIG. 5 illustrates another example embodiment of a heterogenousstructure using conductive gel as a trace according to some inventiveprinciples of this disclosure.

FIG. 6 illustrates another embodiment of structure having a continuousinterconnect according to some inventive principles of this disclosure.

FIGS. 7 and 8 are side and top views, respectively, of an embodiment ofa structure having continuous interconnects between dissimilar materialsaccording to some inventive principles of this disclosure.

FIG. 9 is another side view of the structure of FIGS. 7 and 8.

FIG. 10 is a cross-sectional view of another embodiment of a structurehaving continuous interconnects between dissimilar materials accordingto some inventive principles of this disclosure.

FIG. 11 is a cross-sectional view of another example embodiment of aheterogenous structure according to some inventive principles of thisdisclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates an embodiment of a structure according to some of theinventive principles of this patent disclosure. The system of FIG. 1 mayinclude at least two heterogeneous materials: material A (10) andmaterial B (12). Materials A and B may be dissimilar in that they haveat least one differing mechanical property, constraint, processingparameter, etc. One or more media 14 may extend between materials A andB to form a continuous interconnect between the materials. FIG. 2illustrates another embodiment similar to that of FIG. 1, but theembodiment of FIG. 2 may include a transition A/B (16) between materialsA and B.

Examples of suitable media 14 include viscous, elastic, viscoelasticand/or any other materials that may deform in response to deformation ofone or more of materials A and B and then return to a previous form whenone or more of materials A and B return to a previous form. The mediumor media 14 may return to a previous form through its own action (e.g.,if the medium is an elastic material) or through the action of one ormore of materials A and B returning to a previous form (e.g., if themedium is a fluid).

In some embodiments, the media 14 may include one or more functionalmaterials that may have at least one function that is not primarilystructural, for example, conducting electricity, light, sound, etc.,sensing one or more stimuli such as stress, strain, pressure,temperature, elongation, etc., mass transport (as of the materialitself), thermal transport, mechanical linkage such as transmittingforce, motion, pressure, vibrations, etc., and/or any other type offunction. In some embodiments, a functional material may have at leastone fluid property or component, for example, as a fluid phase materialor a fluid component of a gel material, among others.

In some embodiments, the functional material may be implemented with aviscoelastic material having both a fluid and a solid component. Such amaterial may perform, for example, an electroactive function such asconducting electricity, or it may function as a mechanical interconnect,an actuating interconnect, a fuel line or fluid reservoir or any otherfunction. The viscoelastic interconnect material may be arranged in anysuitable geometry to accommodate any intended function.

In rheology G* may refer to a complex shear modulus which may containtwo components: G′ and G″ which may be referred to as a storage modulusand loss modulus, respectively. The storage modulus may essentiallycharacterize an elastic component of a material, whereas the lossmodulus may characterize a viscous or liquid component of the material.In some embodiments, by selecting a function material to have a higherG′ than one or both of materials A or B, the functional material maysurvive some degree of compression during formation and/or usage of thestructure. In some embodiments, and depending on the implementationdetails, a storage modulus of a functional material may be considered“higher” than a storage modulus of one or both of the materials A or Bif it is higher by an amount that may enable the functional material towithstand compression or other distorting stimulus during formationand/or usage while still remaining functional after formation and/orusage of the structure.

Examples of differing mechanical properties of materials A and B includemodulus (e.g., Young's, shear, bulk, etc.), hardness (Shore, Mohs,Brinell, Rockwell, etc.), strength (e.g., tensile, compressive, etc.),density, etc.

Examples of differing processing parameters of materials A and B includetemperature, pressure, time, reagents (e.g., reactants, solvents,catalysts, activators, etc.), exposure to UV, IR, RF, ultrasoundtreatment, etc.

Examples of differing constraints of materials A and B includedeformation limits (e.g., because of having rigid components mountedthereon, placement on an object such as a human body or sensitivemechanical instrument, etc.), exposure limits (e.g., to temperature,radiation, UV. IR, RF, ultrasound, chemicals, etc.), etc.

The medium or media 14 that form the interconnect may be formed on oneor more surfaces of materials A and/or B or transition A/B, in passagesthrough any of materials A and/or B or transition A/B, or in any otherarrangement that creates an operative interconnect between materials Aand B.

The transition A/B, if any, may include overlap, interleaving, amaterial gradient, and/or the like, between materials A and B, and/orone or more intermediate, transitional, buffer, etc., materials betweenmaterials A and B.

Deformation of one or more of materials A and B, and correspondingdeformation of the interconnect 14 may be in response to any or all oftensile, compressive, stretching, flexing, twisting, bulk, etc., forceson one or more of the materials A and B.

Examples of types of interconnect formed by medium or media 14 mayinclude mechanical, electric, electrical, electronic, electromechanical,electromagnetic, and/or other electro-active interconnect, optical,photonic, audio, mass transport, etc.

Examples of materials suitable for use as materials A and B, in anycombination, may include natural and/or synthetic polymers of any typeincluding rubber and plastic materials such as silicone based materialsincluding polydimethylsiloxane (PDMS), urethanes including thermoplasticpolyurethane (TPU), ethylene propylene diene monomer (EPDM), neoprene,as well as epoxies, pure and alloyed metals, woven or nonwoven fabrics,wood, leather, paper, fiberglass and carbon and other compositematerials, etc., or any combination thereof.

Examples of materials suitable for use as the medium or media 14 thatform the interconnect include, but are not limited to, deformableconductors including conductive gels such as gallium indium alloys, someexamples of which are disclosed in U.S. Patent Application PublicationNo. 2018/0247727 published on Aug. 30, 2018 which is incorporated byreference. Other suitable electroactive materials may include anyconductive metals including gold, nickel, silver, platinum, copper,etc.; semiconductors based on silicon, gallium, germanium, antimony,arsenic, boron, carbon, selenium, sulfur, tellurium, etc.,semiconducting compounds including gallium arsenide, indium antimonide,and oxides of many metals; organic semiconductors; and conductivenonmetallic substances such as graphite. Other examples of conductivegels include gels based on graphite or other forms of carbon and ionicgels. Examples of suitable non-electroactive compositions include manyother types of gels such as, for example, silica gels, and chafing fuelsuch as Sterno, etc. Other examples include liquids such as water, oils,inks, alcohol, etc., any of which may be electroactive or not, as wellas any elastic materials which may be electroactive or not.

Some additional inventive principles of this patent disclosure relate tothe use of a structure such as those illustrated in FIGS. 1 and 2 toserve as an interconnect between heterogeneous materials hosting variousspecialty components in, for example, a deformable electronic assemblysuch as a Flexible Hybrid Electronics (FHE) assembly. In somenon-limiting example embodiments, the interconnect may span heterogenousjunctions between deformable circuit boards such as printed circuitboards (PCBs) like flexible printed circuit boards (FlexPCBs) and/orstretchable PCBs (StretchPCBs) and other deformable structures such as,for example, TPU or Silicone structures. Techniques that may be used toform such structures may include molding, adhesive bonding,thermoforming, tape bonding, ultrasonic bonding, and/or others. In someembodiments, such techniques may be combined with FHE technologies andone or more of the interconnects disclosed in this patent disclosure tocreate one or more integrated textile/electronic assemblies withapplications, for example, in industrial, consumer and/or wearableelectronics.

Mixed mode interconnects, particularly between hard and soft materialsor rigid components and materials that conform into non-rectilinearshapes may present challenges in deformable electronics such as FHE. FHEand other deformable electronics may be applied in Internet-of-things(IoT) and wearable applications in which electronics may existintimately with mechanical elements traditionally considered dissimilarfrom the mechanics of traditional electronic assembly. Materials such asfabric, rubber membranes, thermoformed plastics and similar may directlyintegrate electronic elements in order to support smart or activelycontrolled functionality.

Interconnects between dissimilar materials may be handled with specialtysolders, conductive adhesives or mechanical connectors. However, some ofthese may involve compatibility with separate traces built onto twodissimilar substrates, each of which may have its own mechanicalconstraints. This may involve engineering of both the interconnect andthe mechanics of the dissimilar materials and create substantialconstraints and overhead on the design of an FHE or other deformableelectronic device.

The inventive principles of this patent disclosure may enable potentialinterconnect problems such as multimodal metallization to be bypassed byemploying continuous interconnects produced by conductive gels and/orother conductive functional materials through vias or other passages cutor formed into mixed material substrates, printed directly on thesubstrates, or arranged with the substrates in any other suitablemanner. In some embodiments, continuous circuits including vias andother structures with single and/or mixed material multilayer circuitconstructions may be fabricated with interconnects formed fromconductive gels and/or other conductive functional materials. In someembodiments, components may be directly coupled to traditionalelectronic elements including Surface Mount Components, flex circuitsand conductive fabrics through vias in adhesive substrates that may befilled with conductive gel and/or other conductive functional materials.Both of these constructions may produce ohmic, low impedance contactswith, for example, resistance to strain cycling and/or bend tests and/orwith an ability to tolerate the dynamic loading placed on the structuresboth during final assembly and during use in applications such aswearable electronics, strain monitoring electronics, etc., where dynamicmovement may be expected.

In some embodiments, the inventive principles of this patent disclosuremay be applied to many substrate materials and manufacturing methodsthat may allow both the hosting of rigid Surface Mount Components oneither FlexPCB or StretchPCB substrates and the creation of mechanicallyrobust interconnects attached to the PCB components that would be ableto undergo substantially greater strains all spanned by continuous wiresconstructed from conductive gels.

In some example embodiments, an FHE or other deformable electronicdevice may include both a first substrate portion that hosts surfacemount components and a second substrate portion that functions as arelatively higher elongation textile integrated conductor and/or straingauge produced with, for example, a conductive gel. The higherelongation portion of the circuit may provide a variable resistanceand/or conductive path to the low elongation flex circuit which may hostone or more passive and/or active surface mount technology (SMT)components capable of creating, for example, a visual output of thestretch experienced by the high elongation portion.

Some examples of materials that may be used for an FHE device or otherdeformable device according to some inventive principles of this patentdisclosure include but are not limited to the following: any TPUsincluding, for example, a low Shore A TPU and/or other TPUs with highShore A; thermoset and/or epoxy based films: silicones, for example anytype of curing silicones that may be applied, e.g., to a high stretchknit fabric; copper or metal clad polyamide or other substrates whichmay be used in FlexPCBs, StretchPCBs, and/or the like; and any activeand/or passive through-hole and/or surface mount components. In someexample embodiments, copper clad polyamide and SMC components may beused to form a stable electrical connection to vias filled withconductive gels and may be applied, for example, as components in ahybrid assembly.

FIG. 3 is an exploded perspective view illustrating an exampleembodiment of an interconnect design suitable for use with an FHE deviceor other device according to some inventive principles of this patentdisclosure. Two pads 101 and 102 having diameters D1 and D2,respectively, on separate layers of dissimilar substrates A (103) and B(104), respectively, may be printed, for example, with a hole passingthrough the pads such that electrical continuity is achieved. Pad 101may communicate with trace 107 on Substrate A, and pad 102 maycommunicate with trace 108 on Substrate B.

Pad size and via hole size may be chosen to facilitate design formanufacturability of the circuit board. In some example embodiments ofheterogeneous interconnects on flexible and/or stretchable substrates,the size of these features may be chosen for the expected deformation ofthe substrates and/or to facilitate the assembly & testing of theheterogeneous interconnects. In some embodiments, these via pads may rundirectly to a surface mount component which may be adhered to thesurface or to a pad on a circuit (e.g., a polyamide circuit).

The example of FIG. 3 is shown with a transition substrate A/B (105)having a via 106 with diameter D3 between overlapping portions ofsubstrates A and B, but the transition substrate may be omitted in someembodiments. The materials used for substrates A and B and transitionsubstrate A/B (if used) may be chosen from any of the materialsidentified above or any other suitable materials. The pads, traces andfill material for the vias may be implemented with conductive gels orany other suitable conducting materials.

FIG. 4 is a cross-sectional view of another example embodiment of aheterogenous structure (which in some embodiments may be implemented asa layup) using conductive gel and/or other interconnect medium 114 astraces according to this disclosure. Substrate A (110) may overlap andbe attached directly to Substrate B (112). In other embodiments, atransition substrate may be used. In this embodiment, a via 116 may beformed through Substrate A, for example, because the trace 122 and/orpad 124 on Substrate A may be aligned on top of the trace 118 and/or pad120 on Substrate B, and therefore conductive gel in the via 116 ofSubstrate A may directly contact the pad 120 on top of Substrate B.

The structure illustrated in FIG. 4 may include one or more encapsulantsto constrain and/or protect the traces, pads, and/or vias of conductivegel and/or other interconnect medium 114. For example, at least aportion of Substrate A may be coated with Encapsulant A (126), and atleast a portion of Substrate B may be coated with Encapsulant B (128).Any suitable materials may used for encapsulants, for example, siliconebased materials such as PDMS. TPUs, urethanes, epoxies, polyesters,polyamides, varnishes, and any other material that may provide aprotective coating and/or help hold the assembly together. Thesubstrates 110 and 112 may be bonded together using any suitabletechnique including adhesive bonding, thermoforming, tape bonding,ultrasonic bonding, etc.

Examples of applications in which a structure like that illustrated inFIG. 4 may be useful include applications in which substrate A may beimplemented with a material that may be used to host one or moreelectronic components, whereas substrate B may be implemented with amaterial that may be used to provide a connection to a remote sensor,display, electronic module, etc. For example, substrate A may befabricated from a relatively rigid material, whereas substrate B may befabricated from a relatively flexible and/or stretchable material.

In some embodiments, the trace 122 may be formed on the bottom ofsubstrate A (110), thereby eliminating the via 116. In such anembodiment, encapsulant A (126) may be applied to the bottom surface ofsubstrate A (110). In some embodiments, Encapsulant A (126), andEncapsulant B (128) may be combined as a single component.

In some embodiments, some or all of the structure illustrated in FIG. 4,as well as any of the other structures described in this disclosure, maybe fabricated at least in part using any of the materials and/orfabrication techniques described in U.S. Patent Application PublicationNo. 2020/0066628 published on Feb. 27, 2020 which is incorporated byreference may be used in conjunction with any of the methods and/orarticles of manufacture described herein.

FIG. 5 illustrates another example embodiment of a heterogenousstructure using conductive gel as a trace according to some inventiveprinciples of this patent disclosure. In the embodiment illustrated inFIG. 5, a ribbon of thermoset plastic laminate 130 (material A) mayoverlap a ribbon of TPU 132 (material B) at an overlap region 134 (A/B).A heterogenous interconnect medium made from, for example, eutecticgallium alloy, may have a first portion 136 on material A, a secondportion 138 on material B, and a transition portion 140 in the overlapregion 134. All three portions of the trace may be encapsulated, forexample, with one or more encapsulants such as silicone, TPU, urethane,epoxies, etc.

The thermoset plastic (material A) and TPU (material B) may havesubstantially different mechanical properties which are spanned by thecontinuous conductive trace, thus forming a heterogenous interconnectthat transitions between two heterogeneous materials. For example, insome embodiments, the thermoset plastic laminate (material A) may besubstantially more rigid than the TPU (material B).

An electromechanical connector such as a solderable connector 142 mayoverlap with the second portion 138 of the trace in an overlap region144 to form another heterogeneous electrical connection between thecontinuous trace and any other electric apparatus. Alternatively, insome embodiments, a polyamide layer may be adhered to conductive fabricas a terminal layer to provide an interconnect between conductive gelencapsulated in TPU or Silicone and a solderable connector mechanicallyconnected to the conductive fabric.

FIG. 6 illustrates another embodiment of a structure having a continuousinterconnect according to this disclosure. In the embodiment illustratedin FIG. 6, an outer ring 150 of conductive gel and an inner ring 152 ofconductive gel may be patterned on a first substrate 154 (material A)formed from a relatively rigid material such as thermoset plastic. Thefirst substrate 154 may transition to a second substrate 156 (materialB) formed from a relatively flexible and/or stretchable material such asa silicone. The first substrate 154 and second substrate 156 maytransition through a lap joint, butt joint, or in any other manner. Afirst linear trace 158, which may be electrically connected to the outerring 150, may be patterned on the first substrate 154 and the secondsubstrate 156 so as to span the transition between material A andmaterial B. A second linear trace 160, which may be electricallyconnected to the inner ring 152, may be patterned on the first substrate154 and the second substrate 156 so as to span the transition betweenmaterial A and material B.

One or more two-terminal electronic components such as light emittingdiodes (LEDs) 162, may be mounted on the first substrate 154 with oneterminal in direct contact with each of the inner and outer rings. Thefirst substrate 154 may be encapsulated, for example, with a transparentencapsulant such as silicone to enable the LEDs to be visible throughthe encapsulant. The second substrate may be encapsulated, for example,with another layer of silicone, with the linear traces 158 and 160bonded therebetween. The portions of the linear traces 158 and 160 shownin dashed lines may be covered by the encapsulant on the secondsubstrate 154, which in some embodiments may not be transparent.

In some embodiments, a fabric mesh may be applied to the first substrate154, for example, by including it within the encapsulant, or by bondingwith another encapsulant, to provide selective strain limiting of thefirst substrate 154 and the patterns of conductive gel and LEDs formedthereon.

Thus, the embodiment illustrated in FIG. 6 may provide an electronicassembly in which a relatively rigid, but still flexible and/orstretchable substrate 154 (material A) may provide a base for electroniccomponents, while providing electrical connections to the base through arelatively more flexible and/or stretchable substrate 156 (material B),in some implementations, without the use of any solid wires.

Conductive gels made from gallium alloys such as those described in U.S.Patent Application Publication No. 2018/0247727 may be particularlybeneficial for use with interconnects between heterogeneous materialsbecause they may be patternable on a wide variety of substratesincluding TPU, Silicones, Epoxies, EPDM and various thermosetelastomers. In some embodiments, the patterning method may beessentially graphic in nature and may form a mechanical bond between thesubstrate and conductive gels. In some embodiments, there may be no curestage or chemical reaction which may aid in wetting functional patternsto many substrates. An example is a composition of Gallium-Indium-Tineutectic alloy in which a crosslinked Gallium-Oxide nanostructure hasbeen induced in order to change the viscosity and wetting parameterswhich allows the material to be controllably patterned onto a widevariety of substrates. Eutectic gallium alloy gels may also have nostructure to break down on strain cycling because the material mayconduct in an amorphous fluid state making it robust to strain cyclingup to the limits of its substrate. Thus, they may provide an effectivesolution for interconnects between heterogeneous materials in FHE andmany other applications, particularly in a crucial hard to softtransition. Eutectic gallium alloy gels may also have excellentelectrical properties providing low resistance DC connections andtransmission line parameters (primarily S11) up to 5 Ghz and beyond.

FIGS. 7 and 8 are side and top views, respectively, of an embodiment ofa structure having continuous interconnects between dissimilar materialsaccording to some inventive principles of this patent disclosure.

The embodiment of FIGS. 7 and 8 may include first, second and thirddissimilar substrates 18, 20 and 22. In this example, the firstsubstrate 18 may be a rigid TPU, the second substrate 20 may be a moreflexible but still firm TPU, and the third substrate 22 may be a softTPU, but the inventive principles are not limited to these details, andany combination of materials having various properties may be used. Thefirst and second substrates may be bonded together at junction 19 usingany suitable bonding technique, and the second and third substrates maybe bonded together at junction 21 using any suitable bonding technique.The components in FIGS. 7 and 8 are not necessarily to scale. Forexample, the substrates may be made from very thin sheets of material,in which case the vertical scale of FIGS. 7 and 8 is exaggerated.

A trace of conductive medium such as a conductive gel may be formed in aU-shaped pattern 28 on the upper surfaces of the substrates and crossingover the junctions between the substrates. The ends of the U-shapedpattern 28 may terminate at contact pads 24 and 26 which may beconventional electric contact pads because of the rigid characteristicof the first substrate 18. Although not shown in FIGS. 7 and 8, anencapsulant may be formed over the U-shaped pattern 28 and top surfacesof the substrates 18, 20 and 22.

The resulting structure may be bent in response to various forces withthe different substrates providing different bend radii as shown by R1and R2 in FIG. 9 which is another side view of the structure of FIGS. 7and 8 showing it being deformed. In some embodiments, such a structuremay function as a strain relief.

The structure of FIGS. 7 and 8 may also include transitions betweenother materials such as TPU to epoxy, silicone to epoxy, silicone tofabric or TPU, etc. In some embodiments, and depending on theimplementation details, it may be particularly beneficial to have acontinuous interconnect between TPU and silicone because it tends to bedifficult to make electrical connections to silicone, but relativelyeasy to make electrical connections to TPU. Therefore, electricalconnections may be placed on a TPU substrate which may then transitionto silicone which may provide a more sensitive substrate for a sensormade from deformable conductors such as conductive gels.

In some embodiments, after printing a circuit via a stencil,flexographically or some other deposition process, an encapsulant layerwith deformable conductor filled vias may be added, or the circuitexposed may simply be left exposed. Next, an integrated circuit (IC) orother electronic device may be placed on the circuit. A metal layer onthe IC may form a low impedance, ohmic contact with the conductive gel.In some embodiments, the substrate itself may be adhesive, which maykeep the IC (or a packaged surface mount component (SMC)) in place.Alternative, an adhesive may be placed onto a landing area or onto theIC (or SMC). Finally, an encapsulation layer can be placed over theassembly to hold the conductive gel and IC's in place.

In some embodiments according to the inventive principles of this patentdisclosure, it may be beneficial to any of the soft interconnect attach,direct die attach, direct IC attach and/or soft interconnect COB (chipon board) process to have a very soft/conforming conductor. In someembodiments this may be achieved by using a conductive gel, e.g., aGallium-Indium-Tin alloy with blended in oxides and micron scaleparticles to control viscosity. In some embodiments, such a techniquemay be utilized with other conformal conductors capable of making a lowimpedance contact with a metal layer.

In some other embodiments according to some inventive principles of thispatent disclosure, a gasket made of a material such as EPDM (ethylenePropylene Diene Monomers) may have a pattern of deformable conductorsarranged to sense the performance of the gasket. Since it may berelatively difficult to attach electric contacts to EPDM, the deformableconductors may be coupled through a continuous interconnect between theEPDM gasket and another material such as TPU which may be a goodsubstrate for electric contacts. Thus, a sensing circuit may beconnected to the contacts on the TPU substrate while still providing agood electric connection to the pattern of deformable conductors in oron the EPDM gasket.

FIG. 10 is a cross-sectional view of another embodiment of a structurehaving continuous interconnects between dissimilar materials accordingto some inventive principles of this patent disclosure. The embodimentof FIG. 10 may include a pattern of conductive material 30 formed from ametal clad layer on a first substrate 32. The first substrate 32 may beattached to a second substrate 34 which may have traces 36 of adeformable conductor such as a conductive gel. An encapsulant 38 maycover the second substrate 34 and traces 36. Vias 41 and 43 through thefirst substrate 32 and second substrate 34, respectively, may enable thedeformable conductor to form a continuous interconnect 40 between thepattern of conductive material 30 and the traces 36 on the secondsubstrate 34. Any or all of the layers illustrated in FIG. 10 may haveone or more dissimilar characteristics, and the use of a functionalmaterial such as a conductive gel for the continuous interconnect 40and/or traces 36 may enable the assembly illustrated in FIG. 10 to befabricated and/or operate while eliminating or reducing problemsassociated with material fatigue, material creep, galvanic actionbetween multiple conductors, and/or the like.

The embodiment illustrated in FIG. 10 may, for example, host one or morepassive and/or active SMT components. The SMT component(s) may beattached to the pattern of conductive material 30 using known methods,for example, various soldering techniques. The embodiment illustrated inFIG. 10 be used, for example, in a bio-electric sensor for anelectrocardiogram (ECG or EKG), electromyogram (EMG), and/or the like.In such an embodiment, the conductive material 30 may be fabricated fromconductive silicone, copper cladding, or other material appropriate forimplementing an electrode suitable for contact with a patient's body.The substrates 32 and 34 may be fabricated, for example, from a materialthat may be rigid enough to host one or more electronic components, butflexible enough to comfort comfortably to a patient's body. Examplesinclude TPU, polyamide, thermoset epoxy, thermoset plastics, etc.

In some example embodiments, the conductive material 30 may beimplemented as conductive silicone which may be well-tolerated for skincontact, while the second substrate 34 may be implemented with epoxy toform a base for electronic components and/or other layers of traces fora circuit board. The first layer 32 may be implemented with TPU whichmay protect a patient from contact with the epoxy substrate 34 which maybe an irritant to some patients.

Although the conductive trace 36 is shown on the bottom of the secondsubstrate 34, in some embodiments, the conductive trace 36 may passthrough the second substrate 34 which may serve, for example, as anin-place stencil to form the trace 36 which may be enclosed between thefirst substrate 32 and the encapsulant 38.

Some embodiments may include additional layers of substrates withadditional vias, traces, etc. to form a functional circuit with one ormore electrical and/or electronic components.

In some embodiments, the structure illustrated in FIG. 10 may include aninterface 44 to connect the assembly to one or more other apparatus. Forexample, in some embodiments, the conductive trace 36 may transition toone or more terminals to couple the assembly to a cable or otherconductive apparatus, for example, to read data from a sensor into whichthe assembly is integrated. In other embodiments, the interface 44 maytransition to another heterogeneous junction such as that illustrated inFIG. 4, for example, to transition to a relatively high-elongationconductive assembly to connect the assembly to other apparatus.

In some embodiments, one or more of the substrates illustrated in FIG.10 may be implemented as a fabric layer, or a fabric layer may be addedas an additional layer. Such a fabric layer may be included for example,to provide patient comfort in the case of a bio-electric sensor.Moreover, additionally, or alternatively, such a fabric layer may beused to integrate the assembly into a piece of clothing or apparel, orother wearable apparatus such as a brace. Moreover, multiple assembliessuch as that illustrated in FIG. 10 may be integrated into a single apiece of clothing or apparel, or other wearable apparatus with one ormore flexible and/or stretchable substrates forming electrical and/orelectronic interconnects between the assemblies.

FIG. 11 is a cross-sectional view of another example embodiment of aheterogenous structure according to this disclosure. The embodimentillustrated in FIG. 11 may include components similar to thoseillustrated in the embodiment of FIG. 4, but the embodiment of FIG. 11may further include a third substrate, substrate C (166) forming asecond junction with substrate B (112). A trace 168, trace and/or pad170, via 172, and/or via 174 may continue the continuous interconnectformed by interconnect medium 114 through trace 122 and/or pad 124, via116 and trace 118 and/or pad 120. Another encapsulant C (176) mayencapsulate the portion of the interconnect in or on substrate C. Insome embodiments, any of the encapsulants A, B and/or C may be formed asa single layer.

In some embodiments, the structure illustrated in FIG. 11 may be used,for example, in an application in which it may provide a continuousfunctional interconnect between components X and Y. For example,component X may be implemented as a sensor, display, actuator and/or anyother type of component that may be hosted on substrate A, which may beimplemented, for example, with a material that may be relatively rigidenough to host the sensor, display, actuator, etc., of component X, forexample, as a medical or other bio-sensor, industrial sensor, etc., butstill flexible and/or stretchable enough to conform to a subject's body,piece of industrial equipment, parachute, clothing or other soft good,etc. Substrate A may then transition to substrate B, which may beimplemented, for example, as a relatively more flexible and/orstretchable (e.g., high-elongation) material that may conduct one ormore signals and/or operate as a sensor while extending along a certaindistance to component Y. For example, substrate B may be sewn or bondedinto or otherwise attached to an article of clothing, parachute cord,pipe, conduit, cable, etc. Substrate B may then transition to substrateC which may be implemented, for example, with a relatively rigidmaterial such as a fiberglass or polyamide circuit board which may hosta data collection and/or processing unit that may display data receivedfrom component X, send data to be displayed by component X, control oneor more sub-components in component X, etc.

Thus, in some embodiments, and depending on the implementation details,an assembly such as that illustrated in FIG. 11 may provide a completeend-to-end interconnect solution between two components that may spanmultiple junctions between heterogeneous materials, which in turn maytraverse multiple environments, while utilizing one continuousinterconnect.

Some techniques that may be used for fabricating continuousinterconnects between heterogeneous materials such as those illustratedin FIGS. 10 and 11 according to some inventive principles of this patentdisclosure include those disclosed in the above-mentioned U.S. PatentApplication Publication No. 2020/0066628 which is incorporated byreference, and which discloses methods for direct attachment of surfacemount components to vias filled with a conductive gel and otherinterconnect media, and stenciling methods for manufacture a multi-layerPCB that may be compatible with conductive gels and other interconnectmedia.

Example 1 is a deformable electronic device, comprising: a firstsubstrate portion comprising a metal clad layer; at least one surfacemount component mounted to the first substrate portion and electricallycoupled with the metal clad layer; a second substrate portion, attachedto the first substrate portion, including at least one trace formedthereon with conductive gel; and a via, comprised of conductive gel,extending between and electrically coupling the metal clad layer withthe trace.

In Example 2, the subject matter of Example 1 includes, wherein thefirst substrate comprises a thermoset epoxy-based film.

In Example 3, the subject matter of any one or more of Examples 1 and 2includes, wherein the metal clad layer is comprised of copper.

In Example 4, the subject matter of any one or more of Examples 1-3includes, wherein the first substrate comprises a thermoplasticpolyurethane (TPU).

In Example 5, the subject matter of any one or more of Examples 1-4includes, wherein the first substrate comprises a silicone.

In Example 6, the subject matter of any one or more of Examples 1-5includes, wherein the first substrate portion is bonded to the secondsubstrate portion.

In Example 7, the subject matter of any one or more of Examples 1-6includes, wherein the second substrate forms a stencil to at least inpart form the trace.

In Example 8, the subject matter of any one or more of Examples 1-7includes, an encapsulant configured to enclose the conductive gel withthe second substrate.

In Example 9, the subject matter of any one or more of Examples 1-8includes, wherein at least one of the trace or the metal clad layer isconfigured to electrically couple with an external apparatus.

In Example 10, the subject matter of any one or more of Example 9includes, wherein the surface mount component is one of a passive or anactive component.

Example 11 is a method of making a deformable electronic device,comprising: forming a first substrate portion comprising a metal cladlayer; mounting at least one surface mount component to the firstsubstrate portion and electrically coupling the at least one surfacemount component a with the metal clad layer; attaching a secondsubstrate portion to the first substrate portion, the second substrateportion including at least one trace formed thereon with conductive gel;and forming a via, comprised of conductive gel, extending between andelectrically coupling the metal clad layer with the trace.

In Example 12, the subject matter of Example 11 includes, whereinforming the first substrate comprises forming the first substrateportion with a thermoset epoxy-based film.

In Example 13, the subject matter of any one or more of Examples 11 and12 includes, wherein forming the first substrate comprises forming themetal clad layer of copper.

In Example 14, the subject matter of any one or more of Examples 11-13includes, wherein forming the first substrate comprises forming thefirst substrate portion with a thermoplastic polyurethane (TPU).

In Example 15, the subject matter of any one or more of Examples 11-14includes, wherein forming the first substrate comprises forming thefirst substrate portion with a silicone.

In Example 16, the subject matter of any one or more of Examples 11-15includes, wherein attaching the second substrate portion to the firstsubstrate portion is with bonding bonded.

In Example 17, the subject matter of any one or more of Examples 11-16includes, forming a stencil in the second substrate portion to at leastin part form the trace.

In Example 18, the subject matter of any one or more of Examples 11-17includes, enclosing the conductive gel with and encapsulant and thesecond substrate.

In Example 19, the subject matter of any one or more of Examples 11-18includes, wherein forming the trance includes configuring the trace toelectrically couple with an external apparatus.

In Example 20, the subject matter of any one or more of Example 19includes, wherein the surface mount component is one of a passive or anactive component.

Example 21 is at least one machine-readable medium includinginstructions that, when executed by processing circuitry, cause theprocessing circuitry to perform operations to implement of any ofExamples 1-20.

Example 22 is an apparatus comprising means to implement of any ofExamples 1-20.

Example 23 is a system to implement of any of Examples 1-20.

Example 24 is a method to implement of any of Examples 1-20.

The embodiments disclosed herein may be described in the context ofvarious implementation details, but the principles of this disclosureare not limited these or any other specific details. Some functionalityhas been described as being implemented by certain components, but inother embodiments, the functionality may be distributed betweendifferent systems and components in different locations and havingvarious user interfaces. Certain embodiments have been described ashaving specific components, processes, steps, combinations thereof,and/or the like, but these terms may also encompass embodiments in whicha specific process, step, combinations thereof, and/or the like may beimplemented with multiple components, processes, steps, combinationsthereof, and/or the like, or in which multiple processes, steps,combinations thereof, and/or the like may be integrated into a singleprocess, step, combinations thereof, and/or the like. A reference to acomponent or element may refer to only a portion of the component orelement. The use of terms such as “first” and “second” in thisdisclosure and the claims may only be for purposes of distinguishing thethings they modify and may not indicate any spatial or temporal orderunless apparent otherwise from context. A reference to a first thing maynot imply the existence of a second thing. Moreover, the various detailsand embodiments described above may be combined to produce additionalembodiments according to the inventive principles of this patentdisclosure

Since the inventive principles of this patent disclosure can be modifiedin arrangement and detail without departing from the inventive concepts,such changes and modifications are considered to fall within the scopeof the following claims.

What is claimed is:
 1. A deformable electronic device, comprising: afirst substrate portion comprising a metal clad layer; at least onesurface mount component mounted to the first substrate portion andelectrically coupled with the metal clad layer; a second substrateportion, attached to the first substrate portion, including at least onetrace formed thereon with conductive gel; and a via, comprised ofconductive gel, extending between and electrically coupling the metalclad layer with the trace.
 2. The deformable electronic device of claim1, wherein the first substrate comprises a thermoset epoxy-based film.3. The deformable electronic device of claim 1, wherein the metal cladlayer is comprised of copper.
 4. The deformable electronic device ofclaim 1, wherein the first substrate comprises a thermoplasticpolyurethane (TPU).
 5. The deformable electronic device of claim 1,wherein the first substrate comprises a silicone.
 6. The deformableelectronic device of claim 1, wherein the first substrate portion isbonded to the second substrate portion.
 7. The deformable electronicdevice of claim 1, wherein the second substrate forms a stencil to atleast in part form the trace.
 8. The deformable electronic device ofclaim 1, further comprising an encapsulant configured to enclose theconductive gel with the second substrate.
 9. The deformable electronicdevice of claim 1, wherein at least one of the trace or the metal cladlayer is configured to electrically couple with an external apparatus.10. The deformable electronic device of claim 9, wherein the surfacemount component is one of a passive or an active component.
 11. A methodof making a deformable electronic device, comprising: forming a firstsubstrate portion comprising a metal clad layer; mounting at least onesurface mount component to the first substrate portion and electricallycoupling the at least one surface mount component a with the metal cladlayer; attaching a second substrate portion to the first substrateportion, the second substrate portion including at least one traceformed thereon with conductive gel; and forming a via, comprised ofconductive gel, extending between and electrically coupling the metalclad layer with the trace.
 12. The method of claim 11, wherein formingthe first substrate comprises forming the first substrate portion with athermoset epoxy-based film.
 13. The method of claim 11, wherein formingthe first substrate comprises forming the metal clad layer of copper.14. The method of claim 11, wherein forming the first substratecomprises forming the first substrate portion with a thermoplasticpolyurethane (TPU).
 15. The method of claim 11, wherein forming thefirst substrate comprises forming the first substrate portion with asilicone.
 16. The method of claim 11, wherein attaching the secondsubstrate portion to the first substrate portion is with bonding bonded.17. The method of claim 11, further comprising forming a stencil in thesecond substrate portion to at least in part form the trace.
 18. Themethod of claim 11, further comprising enclosing the conductive gel withand encapsulant and the second substrate.
 19. The method of claim 11,wherein forming the trance includes configuring the trace toelectrically couple with an external apparatus.
 20. The method of claim19, wherein the surface mount component is one of a passive or an activecomponent.